1. Field of the Invention
The present invention relates to a solder connect assembly and a method of connecting a semiconductor package and a printed wiring board, and in particular to a solder connect assembly and a method of connecting a semiconductor package and a printed wiring board for electrically and mechanically connecting a semiconductor package and a printed wiring board through a plurality of solder balls.
2. Description of the Related Art
This kind of a conventional solder connect assembly is disclosed in Japanese Patent Application Laid-Open No. Hei 10-116856. As shown in FIG. 1, in the conventional solder connect assembly, in LSI chip 11 is connected and mounted to/on a ceramic board 12 via solder balls 30 which are external terminals of the LSI chip 11. Also, the ceramic board 12 is similarly connected and mounted to/on a printed wiring board 20 via the solder balls 40 which is an external terminal of the ceramic board 12. After the ceramic board 12 and the printed wiring board 20 are connected via the solder balls 40, clearance between the ceramic board 12 and the printed wiring board 20 is filled with underfiling resin 90.
However, in the conventional solder connect assembly, as the clearance between the ceramic board 12 and the printed wiring beard 20 is filled with underfiling resin 90, there is a problem that the ceramic board 12 cannot be replaced or repaired in case a problem occurs in the ceramic board 12 or the LSI chip 11 after the underfiling resin 90 is cured.
Also, while the underfiling resin 90 is filled utilizing a capillary phenomenon, in the conventional solder connect assembly, there is a problem that a void often occurs in the vicinity of an interface between the solder balls 40 and the printed wiring board 20. When stress is applied to the underfiling resin 90 after its curing, the stress is not reduced enough and the solder balls 40 may be broken.
Further, there is a problem that the solder balls 40 may be broken due to the storage and carriage of the solder balls 40 and stress by heating when the underfiling resin 90 is cured in a process till the filling and curing of the underfiling resin 90.
In addition, in Japanese Patent Application Laid-open No. Hei 8-116169, another conventional solder connect assembly is disclosed.
The conventional solder connect assembly provides a fatigue resistant solder connection for a solder connection structure. The solder connection structure, which couples the facing surfaces of two substrates, is comprised of a compliant metal alloy solder preform connectably disposed between two less compliant metal alloy solder fillets.
Further, an underfiling resin and a resin fillet in a conventional electric device assembly are disclosed in Japanese Application Laid-Open No. Hei 9-167890 and Hei 10-313016, respectively. However, it is not taught in these references that an assembly electrically and mechanically connects a plurality of solder balls and a printed wiring board.
It is therefore an object of the present invention to provide a solder connect assembly and a method of connection capable of enhancing reliability in connection of a solder ball connection.
Another object of the present invention is to provide a solder connect assembly and a method of connection capable of replacing a package or a board for repairing it after connection thereof.
In order to achieve the above objects, a solder connect assembly according to the present invention comprises a printed wiring board, a semiconductor package, a plurality of solder balls disposed between the printed wiring board and the semiconductor package, for connecting the printed wiring board and said semiconductor package, and a resin fillet formed in the vicinity of the printed wiring board and each said solder ball.
Another solder connect assembly according to the present invention comprises a printed wiring board, a electrode formed on the printed wiring board, a semiconductor package, a pad formed on the semiconductor package, a solder ball disposed between the electrode and the pad, and a resin fillet formed on a side of the solder ball.
In order to achieve the above objects, a method of connecting a semiconductor package and a printed wiring board according to the present invention comprises the steps of supplying cream solder on an electrode formed on the printed wiring board, wherein the cream solder includes resin, mounting the semiconductor package on the printed wiring board, heating and melting the cream solder, and cooling and curing the cream solder, thereby a solder ball is formed between the semiconductor package and the printed wiring board.